Quote ${MAKE} when passing in env in case it contains spaces.

Downstream we are wrapping MAKE with a limits(1) call which
interferes with these non-quoted cases.

Sponsored by:	Dell EMC Isilon

Makefile

@@ -221,7 +221,7 @@ SUB_MAKE= `test -x ${MYMAKE} && echo ${MYMAKE} || echo ${MAKE}` \
 SUB_MAKE= ${MAKE} -m ${.CURDIR}/share/mk
 .endif
 
-_MAKE=	PATH=${PATH} MAKE_CMD=${MAKE} ${SUB_MAKE} -f Makefile.inc1 \
+_MAKE=	PATH=${PATH} MAKE_CMD="${MAKE}" ${SUB_MAKE} -f Makefile.inc1 \
 	TARGET=${_TARGET} TARGET_ARCH=${_TARGET_ARCH}
 
 # Only allow meta mode for the whitelisted targets.  See META_TGT_WHITELIST

share/mk/bsd.crunchgen.mk

@@ -114,7 +114,7 @@ CRUNCHENV+= MK_TESTS=no \
 ${OUTPUTS:[1]}: .META
 ${OUTPUTS:[2..-1]}: .NOMETA
 ${OUTPUTS}: ${CONF}
-	MAKE=${MAKE} ${CRUNCHENV:NMK_AUTO_OBJ=*} MAKEOBJDIRPREFIX=${CRUNCHOBJS} \
+	MAKE="${MAKE}" ${CRUNCHENV:NMK_AUTO_OBJ=*} MAKEOBJDIRPREFIX=${CRUNCHOBJS} \
 	    MK_AUTO_OBJ=${MK_AUTO_OBJ} \
 	    ${CRUNCHGEN} -fq -m ${OUTMK} -c ${OUTC} ${CONF}
 	# Avoid redundantly calling 'make objs' which we've done by our

sys/conf/kern.post.mk

@@ -372,7 +372,7 @@ config.ln env.ln hints.ln vers.ln vnode_if.ln:
 REPRO_FLAG="-r"
 .endif
 vers.c: $S/conf/newvers.sh $S/sys/param.h ${SYSTEM_DEP}
-	MAKE=${MAKE} sh $S/conf/newvers.sh ${REPRO_FLAG} ${KERN_IDENT}
+	MAKE="${MAKE}" sh $S/conf/newvers.sh ${REPRO_FLAG} ${KERN_IDENT}
 
 vnode_if.c: $S/tools/vnode_if.awk $S/kern/vnode_if.src
 	${AWK} -f $S/tools/vnode_if.awk $S/kern/vnode_if.src -c